The configuration file filestore-s3.properties that is installed along with the package open-xchange-filestore-s3 is extended with two new template properties:

# Specifies the name of the parent bucket to use. The bucket will be created
# automatically if it not yet exists, however, it's still possible to use an
# already existing one. There are some naming restrictions, please refer to
# http://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html for
# details. Required.
com.openexchange.filestore.s3.[filestoreID].bucketName=

# Defines if path-style-access should be used when accessing the S3 API. If
# not set to true, virtual-hosted-style access is used. Please refer to
# http://docs.aws.amazon.com/AmazonS3/latest/dev/VirtualHosting.html for
# details. Defaults to true.
com.openexchange.filestore.s3.[filestoreID].pathStyleAccess=true